1. Field of the Invention
The present invention relates to a modular sewing machine designed to control auxiliary sewing operation devices of the type comprising a bed on which a work-supporting table is defined, a post rising up from the bed, a support arm extending in cantilevered fashion from the post over the work-supporting table and provided with at least a removable cover, a needle-holding head located at one free end of the support arm and an upper shaft extending longitudinally in the support arm and rotation of which is operated to impart a reciprocating motion, through a connecting rod-crank linkage, to a needle bar slidably guided in a vertical direction in the head.
2. Prior Art
It is known that sewing machines are classified in different classes depending upon their structure and the type of sewing operation for which they are designed. Generally each of such classes involves a base version of the sewing machine and different subclasses, that is machines similar to the base one but provided with some additional devices making them adapted to execute particular working types while maintaining the functional characteristics proper to the base version.
In sewing machines of the traditional type it is not possible to create the different subclasses by merely applying said additional sewing operation devices to a sewing machine corresponding to the base version. In other words, it is necessary to produce many types of sewing machines each designed to execute a given type of sewing operation.
Obviously this condition involves high production and storage costs on the part of the manufacturer as well as important installation costs and maintenance charges on the part of the final user who must have many types of sewing machines at his disposal.
For the purpose of solving these problems sewing machines of the so-called "modular" type have been produced, said machines being conceived so that it is possible to accomplish a ready assembling of auxiliary sewing operation devices and consequently their transformation into different subclasses. To this end such sewing machines are provided with kinematic control mechanisms receiving the movement from the shafts housed in the machine bed and terminating in the region of openings formed in the work-supporting table. These kinematic mechanisms involve important increases in the sewing machine costs as necessarily they are comprised of several members that need to be guided and lubricated. Furthermore such increases in costs are not always justified since the presence of at least part of said kinematic mechanisms often appears superfluous.
It is also to be noted that the costs resulting from the arrangement of said kinematic mechanisms must be multiplied when the modular sewing machines are provided with interchangeable bases. In these cases in fact each of the bases to be associated with the machine must have all the kinematic control mechanisms for the auxiliary sewing operation devices.